Field of the Invention
The present invention relates to the field of equipment for laser drilling, and more specifically to such equipment comprising an optical drill head and a laser module with embedded laser subsystems.
Prior Art
A solution for the problems associated to the use of conventional drilling equipment that employs drilling bits that comprise one or more cutting mechanical elements was the use of laser beams as a mean of drilling wells in the ground.
Thus, U.S. Pat. No. 3,871,485 teaches a drilling process using a laser beam wherein a laser beam generator connected to a voltage generator charged by drilling mud or other liquid that passes through a laser beam slot connected to the drill string is positioned in the wellbore and a crystal reflector is positioned inside the laser beam slot to reflect the beam in an elliptical pattern across the formation to be entered.
U.S. Pat. No. 4,066,138 teaches an apparatus to drill the ground assembled above the ground that drives downward a high power energy laser ring to drill a cylindrical orifice by fusing the successive annular regions of the extraction to be entered in a power level that smashes and ejects the orifice successive layers.
U.S. Pat. No. 4,113,036 teaches a laser drilling method and system to recover fossil fuels wherein a vertical bore is drilled in an underground formation; a laser beam is projected through the vertical bore and reflected horizontally from the orifice through the formation along an array of bores.
U.S. Pat. No. 4,090,572 teaches a process and apparatus for laser-treatment of geological formations where a laser beam is projected through a guide for the light beam in a wellbore along a beam guide providing enough laser energy to melt or vaporize formations under underground conditions.
Despite all advantages associated to the use of this drilling method, which is not based on the physical contact between the drill bit and the surface to be drilled, and that presents other advantages, such as a higher speed of penetration, lack of physical contact between the drilling bit and the surface to be drilled, and energy efficiency to name a few, the utilization of lasers to drill wells was not developed at trade levels in function of and due to the lack of lasers with minimal power needed for efficient and competitive drilling when compared to mechanical equipment.
Another problem that has limited the practical implementation of laser-drilling is the large dimension of conventional lasers, which makes impossible their insertion into the drilled wellbores. Another current limitation is the nonexistence of efficient (with low losses by confinement, high transparency, and control of susceptibility to nonlinear phenomenon induction) optical conductors (optical fibers) that allow the guidance of the laser light through long distances and in places with small dimensions and difficult access.
U.S. Pat. No. 5,107,936 teaches a hot-drilling process that employs laser beams as heat source in which the bore hole profile is melted by the heat source and, during the drilling process, the resulting molten rock is pressed against the surrounding sidewall of the well.
In the late 1990s and early 2000s compact and high power lasers became commercially available, and the interest in its utilization for well drilling was renewed. Despite the development of high power lasers (based on different types and active materials, for example, gas, dyes, semiconductors, crystal, optical fiber doped or not, etc.) the development of optical fibers (mono-mode, multi-mode and with several profiles of the cross-section, index of refraction, and materials) with high transparency, low confinement losses and control of nonlinearities constitute other motivating factors to use high intensity laser light for drilling.
With the use of optical fibers it is possible to guide the high intensity laser light to long distances (some tens of kilometers) and keep the laser light quality (temporal and special intensity and coherencies) in the fiber outlet sufficiently high, ensuring the delivery of high optical densities—a condition that increases the drilling process efficiency.
In this regard, the patent literature includes the following recent documents about the subject matter.
U.S. Pat. No. 6,365,871 relates to a laser drilling method through the tool as a nozzle (40), in a cavity that comprises the drilling bore (41) through the tool (40) with the laser (50), providing fluid with laser barrier properties in the cavity so, when the bore (41) is open for the cavity, the laser light passing through the bore (41) is incident over the fluid whereby the tool (40) transversal to the cavity from the bore (41) is protected from the laser light, and causing the fluid to not enter in the drilled bore (41) by laser during the drilling process. The apparatus to perform the method is also described.
U.S. Pat. No. 6,626,249 describes a drilling and recovery geothermal system that comprises a drilling rig having a riser with laser and radar perforation assembled in said elevator, drilling pipe, rotatory mirror assembled adjacent to the lower end of said drilling pipe and devices to establish vacuum adjacent to said lower end of the drilling pipe in order to remover and recover heat and drilling waste.
U.S. Pat. No. 6,755,262 relates to a well drilling apparatus that can be at least partially placed in a drilling well. The apparatus includes a plurality (bundle) of optical fibers. Light energy that is input at one end of each fiber is transmitted through all of them, leaving the bundle to impinge upon at least one lens. The focal lens contains a plurality of focal elements, each one of them arranged to receive the output light energy of at least one of the optical fibers in the bundle, focusing the combined light energy beam in order to break and melt rock.
U.S. Pat. No. 6,870,128 describes the well drilling method with laser beam, the method comprising guiding the laser beam inside a conduit, where the laser beam is guided through the conduit by internal reflectivity of said conduit, and extending the conduit inside the well, so that the laser beam exiting the conduit is guided over to the area in the well to be drilled. A system for drilling a well with a laser beam is also provided, the system comprising a device to guide the laser beam inside the conduit, wherein the laser beam is guided through the conduit by internal reflectivity of said conduit, and device to extend the conduit inside the well, so the laser beam exiting the conduit is guided to an area in the well to be drilled. The invention further provides an apparatus composed of a conduit that can be extended inside the well, and the surface inside the conduit, where the internal surface is reflective to the laser beam.
U.S. Pat. No. 6,888,097 B2 describes an apparatus for drilling holes in the lateral wall of a well, the apparatus including an optical fiber cable with an end for laser input and an end for laser output. A source of laser is connected to the end of the laser input and a laser head is connected to the end of the laser output. The laser head includes a laser control component to control at least a feature of the laser beam. Control elements in the laser head to control the movement and localization of the laser head are connected to the optical fiber cable. The laser head is protected in a slot that protects the optical fiber cable and elements as reflectors and lens to control the laser beam emitted by optical fiber cable there arranged, from the aggressive environment found in underground operations.
U.S. Pat. No. 7,147,064 describes a drilling apparatus to drill a well having a drilling bit set that includes a laser cutting assembly and a vacuum assembly. The vacuum assembly is adapted to collect gases generated by the laser cutting assembly near the drilling bit set during the drilling operation. A chromatographic analyzer can thus be applied to process the collected gases in order to determine features of the rock formation being drilled.
U.S. Pat. No. 7,487,834 describes a method for well drilling with a high power laser intended to provide a laser beam to the well production zone in order to perforate the casing, cement layer, and reservoir rock, generating high permeability lateral penetrations in the formation to increase gas and/or oil flow into the well. An optical fiber cable delivers the laser beam to the laser perforator positioned in the production zone. The cable is curved at an angle around 90 degrees and arranged in the desired beam orientation and profile. A cutting nozzle in the perforating end provides a cleaning flow to: 1) remove from the well droplets of molten metal, cement, and rock fragments that can block the laser beam; and 2) create a free pathway through the well liquids, allowing the beam to reach the target surface during perforating.
U.S. Pat. No. 7,416,258 describes equipment and a method to use lasers in order to break and drill rocks. A group of laser beams is steered in a controlled way by an electro-optical key onto locations at the rock surface, creating multiple holes and removing a layer of rock with the desired diameter. Only a single laser beam, irradiating about 1000 to 5000 W/cm2, spalls the rock. Breaking consecutive layers of rock through an intermittent motion of the laser head, in a direction perpendicular to the surface just drilled, increases depth of the borehole.
US Patent Publication No. 20100078414 A1 relates to an apparatus for underground drilling having at least one optical fiber to transmit light energy from an energy laser source arranged above the ground towards an underground drilling location and a mechanical drill bit having at least one cutting surface and forming at least a light transmission channel aligned to transmit the light from at least one optical fiber through a mechanical drill bit using at least one light transmission channel. It is alleged the equipment developed is especially proper for non-vertical wells.
U.S. Pat. No. 9,062,499 of the same authors of the present document, describes an optical drill head (104) integrated to a laser drilling system. However, this patent does not describe details of said optical drill head.
It is important to highlight that even in the inventions that propose the use of optical fiber(s) to deliver high intensity laser light to the bottom hole of a well, there is no practical demonstration of this possibility when long lengths of fiber are considered (deep wells, i.e., >hundreds of meters). The main reason for this is the non-linear phenomenon induced during high intensity laser light propagation through long lengths of fiber, which is responsible for attenuating the guided light, degrading fiber transparency, and, depending on the energy density and/or peak energy inside the fiber, generating permanent damage in the optical fiber. This is a classic problem in the field of guided optics, and many research groups and companies have been making efforts to reduce or eliminate them. In this respect, see the summary by A. Mendes and T. F. Morse, “Specialty Optical Fibers Handbook”, Chapter 22, pp. 671-696, Elsevier Publisher, 2007.
Among several laser technologies, it is important to highlight the optical fiber-laser development, where high intensity laser light is generated inside the optical fiber itself. This laser is compact and in general does not require cooling, even when operating with high intensities (≧1 kW). Furthermore, light intensity losses generated when coupling the laser outlet to the conducting optical fiber (responsible for guiding the high intensity laser light through long distances up to the region of interest) are now minimal, as, in the case of fiber lasers, there is a fiber-fiber coupling instead of one of fiber with free space.
Regarding the laser light wavelength, it is noted the commercial availability of high power lasers with various different wavelengths (from ultraviolet to infrared, depending on the active element and on the laser cavity design), and of lasers with tunable wavelength. This means that, depending on the material to be drilled, it is possible to use the drilling wavelength coinciding with the absorption range of this material. This significantly increases the process efficiency. Thus, during the drilling it is possible to select in real time the more appropriate laser light wavelength to the material being drilled. This is another technological advantage of laser drilling over the conventional mechanical systems employed today in the oil and gas industry.
Therefore, it would be advantageous that the art had one laser drilling equipment able to generate high intensity light in a downhole module with embedded lasers, such light being guided through optical fibers, along a distance short enough to avoid undesirable nonlinear effects, up to one optical drill head, such head being the mechanical component that supports optical fibers, provides geometrical control to high intensity light action and promotes the drilling system interface with the rock surface to be drilled.
Regarding the researched literature, no documents anticipating or suggesting the teachings of the present invention were obtained, so the solution here proposed has novelty and inventive step toward to the state of the art.